This invention relates to improvements in oil well pumps and more particularly, but not by way of limitation, to a reciprocating subsurface oil well pump.
A typical submerged oil well plunger type pump of the displacement type consists of a plunger and travelling check valve that is reciprocatingly received within a stationary working barrel formed as a part of the oil well production tubing. The working barrel itself is provided with a standing valve and is submerged usually in well fluid.
In one embodiment, the pump is normally secured to the lowermost end of a sucker rod string, which extends longitudinally through production tubing situated in the well bore. A reciprocating device at the surface is usually a `horsehead` type which alternately raises and lowers the string of sucker rods in the well bore. Subsurface pumps have long presented problems in the lifting of the well fluid to the surface of the ground in that the plunger of the pump is usually several feet long and thus requires a relatively long stroke for operation of the pump. This results in substantially great friction and drag on the pump as the pump plunger reciprocates within the working barrel. As a result, the pump plunger may not move freely nor provide a full stroke, thus reducing the pumping efficiency. In addition, since most of the subsurface pumps are relatively long, it may require several strokes of the pump before a sufficient load is applied to the pump to start the pumping action. Also, many well fluids contain sand and other foreign particles which hinder the operation of the subsurface pump and frequently damage the working parts thereof.
Newer forms of pump systems utilize a reciprocating wire line mechanism. A wire line winch provided at the surface will replace the horsehead type apparatus. Such a system includes control means for rotating the winch in one direction for the upstroke and controllably releasing the winch in the reverse direction for the downstroke. In such a system a weighted oil well plunger type pump must be capable, during the upstroke, of providing adequate ring seals for producing the fluid, while on the downstroke, the seal rings must be capable of permitting substantial release of the plunger so that it will fall to its bottom dead center position for the repeat of the process.
Pump plungers of the prior art have been provided with the various means for affecting the necessary fluid seal between the plunger and the working barrel. Such devices are shown in the aforesaid patents cited above. See also U.S. Pat. No. 3,953,155. In many of the prior art plunger pumps, the seal means between the plunger and the working barrel are apt to lose their close tolerance fit because of wear and, therefore, must be pulled occasionally to replace the parts. The pulling operation causes down-time on the well and expense in making the necessary repairs.